JP-A-2003-284393, JP-A-2003-21046, JP-A-2003-327678, and JP-A-2003-278637 disclose generators for generating electric power using natural energy such as wind power. In such a generator, a rotating shaft to be rotated by wind power is connected to a dynamo to convert kinetic energy into electric power of electric energy. The generator includes therein a power supply unit in which a battery is charged with the electric power as power supply for various devices such as electric lights. Thereby, the generator can stably supply electric power irrespective of presence/absence of wind or a change in wind.
However, charging is performed with a high charging voltage upon a strong wind for example, while charging is performed with a low charging voltage upon a weak wind. Thus, the battery is charged with the charging voltage that may change widely. There is a problem that such a conventional generator is low in charging efficiency.
In addition, natural energy is very unstable energy. If electric power is continuously supplied to an external load while no electric power is supplied from the generator for a long time or when the electric power that can be obtained from natural energy is insufficient in itself for the external load, the battery may be over discharged. This causes a problem of shortening the life of the battery.
Further, in case that a state of windlessness continues for a long time, even while power supply to external devices is stopped, the discharge of the battery goes on and the charging voltage is extremely lowered. This causes a problem of bringing about a trouble in which an external controller erroneously operates or can not operate because of electric power of a too low voltage.
Further, in case that the rotating shaft to be rotated by wind power is connected to the dynamo for electric power generation, the rotating shaft must bear the load for operating the dynamo. In this case, when the wind power is weak in comparison with the load, the wind turbine may stop. This causes a problem of making sufficient generation impossible.
Further, if the maximum electric current is always supplied continuously from the start of an operation of an electromagnetic clutch, which is provided for idling the wind turbine upon a breeze, to the end of the operation of the clutch, the consumption of the supplied current is large. This causes a problem of decreasing the gain to the electric power obtained from the dynamo.
Therefore, a first object of the present invention is to make it possible to efficiently charge the battery even in case that the charging voltage changes widely because of a change in wind power.
A second object of the present invention is to prevent storage means from being over discharged even in case of unstable electric power supplied from generating means, and to protect thereby the storage means.
A third object of the present invention is to keep the battery in the charging voltage of a predetermined value or more even in case that a state of windlessness continues for a long time.
A fifth object of the present invention is to make it possible to realize sufficient generation of electric power even in case of small natural energy.
A fifth object of the present invention is to make it possible to realize effective generation of electric power.